Inter-stage steam separator-superheater apparatus for turbines operating with saturated steam

ABSTRACT

An inter-stage steam separator-superheater apparatus whose separator is annular and whose multi-tube steam superheater is mounted inside the separator and coaxially therewith, the plurality of the helically coiled heat exchange tubes, extending along multiple helices, of the steam superheater, the steam to be superheated being directed into the spaces between this plurality of the helically coiled heat exchange tubes, and the heating steam being directed into these helically coiled heat exchange tubes.

United States Patent Andreev et al.

[54] INTER-STAGE STEAM SEPARATOR- SUPERHEATER APPARATUS FOR TURBINES OPERATING WITH SATURATED STEAM prospekt 7, kv. 5, Kharkov; Leonid Alexandrovich Shubenko-Shubin, Sumskaya ulitsa, 69, kv. 21, Kharkov, all of U.S.S.R.

[22] Filed: Sept. 4, 1970 [21] Appl. No.: 69,713

[ 51 Sept. 26, 1972 [52] US Cl ..l22/483, 122/488 51] int. Cl ..F22g 5/16 [58] Field of Search 122/32, 34, 483, 488

[56] References Cited UNITED STATES PATENTS 3,472,209 10/1969 Roffler ..122/483 X 1,839,133 12/1931 Uhde ..l22/483 1,883,605 10/1932 Davy ..l22/483 X 3,500,796 3/l970 Roffler ..l22/483 X Primary ExaminerKenneth W. Sprague Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT An inter-stage steam separator-superheater apparatus whose separator is annular and whose multi-tube steam superheater is mounted inside the separator and coaxially therewith, the plurality of the helically coiled heat exchange tubes, extending along multiple helices, of the steam superheater, the steam to be superheated being directed into the spaces between this plurality of the helically coiled heat exchange tubes, and the heating steam being directed into these helically coiled heat exchange tubes.

8 Claims, 2 Drawing Figures INTER-STAGE STEAM SEPARATOR- SUPERHEATER APPARATUS FOR TURBINES OPERATING WITH SATURATED STEAM The present invention relates to apparatus for the inter-stage drying of steam, incorporated into the structure of high-power turbines operating with saturated steam and, more particularly, it relates to inter-stage steam separators-superheaters for the saturated steam turbines of nuclear power stations.

There are known structures of inter-stage steam separators-superheaters (i.e., of steam separators and steam superheaters structurally combined within a single strong body) which have been developed by the Westinghouse Corporation. In apparatus of this kind steam separation is carried out at separation members including wire grips mounted inside the body of the apparatus, upstream of the tubular heat exchange surface of the steam superheater, the surface being provided by eitherstraight or U-shaped tubes. There are also known inter-stage separator structures of a multi-panel type (the Oyster Creek Power Station); also known are steam superheaters with their heat exchange surface including helically coiled tubes (the Sithwell Power Station). However, these last-mentioned separators and superheaters have not been combined as a unitary separator-superheater structure; they have been so far constructed as independent structures mounted in the engine room of a power station.

One can consider as the drawbacks of these known apparatus their comparatively great structural dimensions, and, consequently, their great steam volumes. This last feature is of a singular importance, since it increases the danger of the turbine running beyond its set speed limits, when the load is disconnected therefrom, and the stop valve of the steam supply operates. This is exactly why some manufacturers install large-diameter cut-off valves at the steam inlets of the low-pressure cylinders of their turbines, in order to guarantee safe operation of the turbines and protect them against the abovedescribed eventuality.

It is an object of the present invention to overcome these drawbacks.

The present invention has for its aim the provision of an inter-stage steam separator-superheater apparatus, which is a relatively compact structure, has a minimal steam volume, features a reduced amount of structural materials going into the manufacture thereof and also features a relatively small (not in excess of 5 to 6 percent the inlet pressure value) value of aerodynamical resistance to the progress of the steam being heated through the apparatus, all this being attained by to a novel structural association of the separator and the steam superheater, and also to the novel construction of the steam separator-superheater apparatus.

This aim is attained in an inter-stage steam separatorsuperheater apparatus for steam power turbines adapted to operate with saturated steam, wherein the steam to be heated is directed to the spaces between the plurality of the helically coiled heat exchange tubes of the superheater and the heating steam is directed into these helically coiled heat exchange tubes, in which apparatus, in accordance with the present invention, the separator is of an annular structure, said multitube steam superheater being mounted inside said separator, coaxially therewith, said plurality of said helically coiled heat exchange tubes of said steam superheater extending along multiple helices.

According to a preferred embodiment of the present invention, it is preferred that plurality of said helically coiled heat exchange tubes of said steam superheater be divided into several sections, the heating steam being supplied independently into each said section and the condensate being independently delivered therefrom.

The hereinafter disclosed inter-stage steam separator-superheater, preferably, for the turbines of nuclear power stations, adapted to operate with saturated steam, is designed to perform drying and subsequent superheating of the steam between the high-pressure stage and the low-pressure stage of the turbine. Separation of moisture-containing steam combing from the high-pressure stage of the turbine takes place in a louvre-type separator mounted within the same body as the superheater. The superheater may be either of a single-stage structure, or of a multi-stage, e.g., a twostage structure; in the last-mentioned case, superheating of the steam which has been dried in the separator to a moisture content of about 1 percent is performed in the first stage by the heat taken from the steam supplied from the extraction point of the turbine, and in the second stage by the heat taken from the steam supplied either from the higher-pressure extraction point, or else by live steam directed from the check valve connections of the turbine.

Among the advantages offered by the structureof a unitary steam separator-superheater apparatus embodying the present invention are the following:

high unit capacity of the separator-superheater apparatus, which makes it possible to operate with a minimal apparatus for normal operation of a turbine;

considerable reduction of the size of such apparatus, as compared with other known kinds of similar apparatus of the same thermal capacity, whereby it becomes feasible to arrange the separator-superheater directly under the turbine; 1

low aerodynamic resistance of the apparatus, as far as the passage therethrough of the steam being superheated is concerned;

minimal volume of the steam to be superheated, filling the separator-superheater;

minimal volume of the steam conduits through which the steam being superheated is to be conducted;

relatively small amount of structural materials needed for the manufacture of such separator-superheater;

facilitated manufacture of such separator-superheater apparatus, with provisions for unification of the technology of production of such separator-superheater of various capacities, as unitary structures, as well as of their individual assemblies;

provisions for establishing at a manufacturing plant a complete production line for series production of such separator-superheater;

provisions for stopping at both ends a defective heat exchange tube without the necessity of opening the internal space of the separator-superheater apparatus and of dismantling the main steam conduit, which simplifies greatly any repairs of the apparatus and minimizes the downtime.

v The present invention will be better understood from the following detailed description of an embodiment thereof, with due reference being had to the accompanying drawings, wherein:

FIG. 1 is a schematic axial sectional view of a steam separator-superheater apparatus, constructed in accordance with the present invention; and

FIG. 2 is a cross-sectional view of the steam separator-superheater apparatus of FIG. 1.

Referring now in particular to the appended drawings, the separator-superheater, constructed in accordance with the present invention, comprises a separator 1 of a multi-panel (louvre) type made up of several individual pluralities of stacked and spaced panels and a steam superheater 2 comprising a plurality of helically coiled tubes, laterally arranged in the stream of the steam to be superheated. The herein disclosed separator-superheater also includes an upper steam-supply chamber 3, an annular passage 4 and a distributing arrangement 5 providing for uniform distribution of the steam to be dried between the sections of the louvres'6 which latter extend along the whole vertical dimension of the inlet portion of the superheating coiled tubes. The vertically stacked sections of the louvres 6 are each associated with a corresponding one of a plurality of troughs 7 adapted to receive thereinside the moisture separated in the louvre sections, i.e., the separate. Circumferentially spaced hollow uprights 8 of the framework of the herein described separatorsuperheater are adapted to serve additionally as drainage conduits through which the separate flows from the respective troughs 7 of the louvres sections 6. Disposed at the bottom of the separator 1 is an annular space 9 serving as a receiver of the separate from the passages inside the uprights 8, the separate leaving this space through a conduit 10. The superheater 2 comprises a sufficient plurality of multi-turn helical coils, either flat or inclined (tapered), connected in parallel to a source of the heating steam. The coils may include either smooth or finned tubes. In the case of inclined coils, they should be of a single-row structure (for drainage of the condensate from the coils, when the herein described separator-superheater is not ,operating), whereas flat coils may be of a multi-row structure. The central space 11 of the herein described separatorsuperheater serves as the outlet chamber for the steam heated in the steam superheater 2. The steam superheater 2 can be arranged to perform either single-stage or multi-stage superheating of the steam, with the plurality of the coiled tubes of the superheater 2 being connected, respectively, either as a single stage or as several stages, each such stage having its own inlet and outlet for the heating fluid. All the end portions of the helically coiled tubes are secured to terminal banks, respectively, in the inlet and the outlet chambers 12, 13 arranged adjacent to the bottom portion of the separator-superheater, the tubes communicating with the internal spaces of the chambers 12, 13 and making fluidtight connections with the terminal banks. Thus, in case of breakage, each tube may be plugged from both ends thereof without the necessity of opening the casing of the separator-superheater for the purpose (and without the necessity of entering the separator-superheater to perform the plugging operation), because both chambers 12 and 13, and, correspondingly, the terminal banks thereof are readily accessible from the outside.

A stream of steam to be dried and consequently superheated is directed from a high-pressure stage of the turbine to the herein disclosed separator-superheater through a steam connection communicating directly with the supply chamber 3, wherefrom it flows into the annular passage 4, and the distributing arrangement 5 distributes the steam uniformly between the louvres 6 of the separator 1. The moisture separated from the steam in the sections of the louvres 6, i.e. the separate, flows by gravity into the throughs 7, wherefrom it travels through the drainage conduits 8 into the space 9 and leaves the separator-superheater through the conduit, or conduits 10 (it may be directed therefrom, e.g., into a system of regenerative heating of the feed water). After having been sufficiently dried in the separator 1, the steam flows directly into the spaces between the heating tubes of the superheater 2, where it is heated to a predetermined temperature and arrives in the central cylindrical space 11, wherefrom it passes through the steam outlet disposed at the top of the structure toward the cylinder of the lowpressure stage of the turbine. The herein described separator-superheater being connected intermediate of the high-pressure and low-pressure stages of the turbine, the steam is driven therethrough by the pressure which is defined by the difference between the respective pressures at the inlet of the separator-superheater and at the condenser of the turbine.

The heating fluid, or the heating steam is supplied to the respective inlet chambers 12 of each of the heating sections of the superheater 2 and flows through the tubes of the respective sections. The heating steam transferring a portion of its thermal energy to the steam being superheated, the former is partly condensated in the tubes of the superheater coils, and the condensate is collected in the condensate chambers 13 of the respective sections, through which it leaves the herein described separator-superheater (it leaves for one of the heat exchange structures of the low-pressure stage, in accordance with the thermal layout adopted by the power station in question, e.g., into the regenerative heater of the feed water, into the deaerator, or else directly into the condenser). The heating steam may be either the live steam supplied from the stop valve connection of the turbine, or steam extracted from the corresponding stages of the turbine, or both depending on the adopted number of superheating stages and on the thermal layout of the power station. The heating steam is positively driven through the superheater 2 under a pressure defined by the difference of the pressure at the inlet of the tubes of the superheater and the pressure in that one of the heat-exchange structures into which the condensate of this heating steam is directed from the superheater.

The model structure of an inter-stage separator-superheater, constructed in accordance with the present invention, performing two-stage superheating of steam in a superheater having its heat exchange tubes in the form of flat multi-row helical coils and calculated for 1 10 to mW of turbine power has made it possible to effect the following results to reduce the total weight of the construction materials by 30 percent; to reduce the total steam volume by 40 percent and to reduce the structural volume by 30 percent, as compared with the horizontal-type double-body separators-superheaters of the same thermal capacity. Moreover, the

aerodynamic resistance of the model separator-superheater has never exceeded 6 percent of the initial pressure of the steam being superheated, whereby the efficiency factor of the associated turbine has been increased by 1.5 percent. A comparison of the major parameters of the various known structures of similar apparatus, has shown that the incorporation of interstage steam separators-superheaters, constructed in accordance with the present invention, into the structure of power stations, particularly, nuclear power stations, can yield substantial economy.

What we claim is: 1. An inter-stage steam separatorsuperheater apparatus for power turbine operating with saturated steam, comprising: a separator constituted as an annular structure; a multi-tube steam superheater arranged internally of said separator and coaxially therewith; said superheater including a plurality of helically coiled heat exchange tubes extending along multiple helices; means for supply steam to be heated through said separator and into the spaces between said plurality of said helically coiled heat exchange tubes of said steam superheater; and means for supplying heating steam into said plurality of said helically coiled heat exchange tubes of said steam superheater.

2. Apparatus as claimed in claim 1 wherein said plurality of said helically coiled heat exchange tubes is of a multi-section structure, each section being associated with respective independent means for introducing said heating steam thereinto and for delivering the condensate therefrom.

3. Apparatus as claimed in claim 1 wherein said annular structure of said separator comprises a plurality of vertically superposed louvre sections.

4. Apparatus as claimed in claim 3 wherein said annular structure further comprises an annular trough connected to each lourve section at the lower end thereof for collection of condensate, and vertical, hollow uprights connecting said troughs and providing passageways for the flow of condensate from said troughs, and means to receive the condensate from the troughs for conveyance externally of the apparatus.

5. Apparatus as claimed in claim 3 comprising a housing surrounding said separator and defining an annular chamber therewith in which the steam to be heated is introduced.

6. Apparatus as claimed in claim 5 wherein said housing is vertical and cylindrical. 

2. Apparatus as claimed in claim 1 wherein said plurality of said helically coiled heat exchange tubes is of a multi-section structure, each section being associated with respective independent means for introducing said heating steam thereinto and for delivering the condensate therefrom.
 3. Apparatus as claimed in claim 1 wherein said annular structure of said separator comprises a plurality of vertically superposed louvre sections.
 4. Apparatus as claimed in claim 3 wherein said annular structure further comprises an annular trough connected to each lourve section at the lower end thereof for collection of condensate, and vertical, hollow uprights connecting said troughs and providing passageways for the flow of condensate from said troughs, and means to receive the condensate from the troughs for conveyance externally of the apparatus.
 5. Apparatus as claimed in claim 3 comprising a housing surrounding said separator and defining an annular chamber therewith in which the steam to be heated is introduced.
 6. Apparatus as claimed in claim 5 wherein said housing is vertical and cylindrical.
 7. Apparatus as claimed in claim 6 wherein said heat exchange tubes are helically coiled internally of the louvre sections in concentric arrangement therewithin, the steam to be heated flowing radially inwards from said annular chamber through the separator and into said superheater.
 8. Apparatus as claimed in claim 1 wherein said heating steam is supplied to said helically coiled heat exchange tubes at the inner ends thereof and flows outwardly in counterflow with the steam to be heated. 